This invention relates to a liquid jetting apparatus having a head capable of jetting a drop of liquid from a nozzle. In particular, this invention is related to a liquid jetting apparatus that can prevent the viscosity of liquid in a nozzle of a head from increasing.
In an ink-jetting recording apparatus such as an ink-jetting printer or an ink-jetting plotter (a kind of liquid jetting apparatus), a recording head (head) can be moved in a main scanning direction, and a recording paper (a kind of recording medium) can be moved in a sub-scanning direction perpendicular to the main scanning direction. While the recording head is moved in the main scanning direction, a drop of ink can be jetted from a nozzle of the recording head onto the recording paper. Thus, an image including a character or the like can be recorded on the recording paper. For example, the drop of ink can be jetted by changing pressure of the ink in a pressure chamber communicating with the nozzle.
The pressure of the ink may be changed by utilizing a pressure-generating member, for example a piezoelectric vibrating member. In such a case, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, the pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is jetted from the nozzle.
The ink in the nozzles of the recording head is exposed to air. Thus, a solvent of the ink, such as water, may gradually evaporate to increase the viscosity of the ink in the nozzle. In that case, the quality of recorded images may deteriorate because ink having a great viscosity may be jetted in a direction that deviates from the normal direction.
To prevent the viscosity of the ink in the nozzles from increasing, some measures have been proposed. One of the measures is to forcibly cause ink having an increased viscosity to jet out from the nozzle outside an objective recording area (a flushing operation). Another one of the measures is to cause a meniscus of the ink to minutely vibrate to stir the ink (a stirring operation). The meniscus means a free surface of the ink exposed at an opening of the nozzle.
The execution amount of such a maintenance operation (the flushing operation, stirring operation or the like) may be set suitably for the quality of images recorded in the objective recording area in order to ensure the quality even at a position in the objective recording area furthest away from a waiting position of the recording head.
However, in the recording apparatus for printing onto a recording paper having a larger size, such as a trimmed B-0 size (1030 mmxc3x971456 mm:JIS P 0138), a distance for which the recording head is moved in the main scanning direction is very long. Thus, when a flushing operation is conducted as a maintenance operation, the volume of the ink jetted from the nozzle in the flushing operation is set to be large in order to ensure that a first drop of ink can be normally jetted even when the first drop of ink is jetted at the position in the objective recording area furthest away from the waiting position of the recording head. Similarly, when a minutely-vibrating (stirring) operation is conducted as a maintenance operation, the number of operations (vibrations) of the pressure-generating member is set to be large.
Thus, if the flushing operation is conducted in the recording apparatus, as the volume of the ink jetted in the flushing operation is large, the volume of the ink used for recording is relatively small. In addition, a waste-ink absorbing unit arranged for collecting the ink jetted in the flushing operation has to have a larger capacity.
In addition, if the minutely-vibrating operation is conducted in the recording apparatus, as the number of the operations (vibrations) of the pressure-generating member is large, the lifetime of the recording head is short.
The object of this invention is to solve the above problems, that is, to provide a liquid jetting apparatus such as an ink-jet recording apparatus that can more efficiently conduct a maintenance operation for preventing the viscosity of ink in a nozzle from increasing in order to keep good conditions condition for jetting a drop of the ink.
In order to achieve the object, a liquid jetting apparatus includes a head having a nozzle adapted to receive jetting data corresponding to one scanning movement in a main scanning direction. A head-scanning mechanism moves the head in the main scanning direction after the head has received the jetting data. A recovering unit recovers a suitable viscosity of liquid in the nozzle from an increased viscosity thereof. A measuring timer measures at least a part of the time since a previous operation of the recovering unit has been completed and a controller controls the recovering unit based on the time measured by the measuring timer.
According to the above features, since the recovering unit is controlled based on at least a part of the time since the previous operation of the recovering unit has been completed, a maintenance operation for recovering the suitable viscosity of the liquid in the nozzle can be conducted more efficiently, dependently on a state of the liquid in the nozzle.
For example, the part of the time since the previous operation of the recovering unit has been completed may be a time since the previous operation of the recovering unit has been completed until the head completes receiving the jetting data. In that case, preferably, a next operation of the recovering unit is conducted just after the head has completed receiving the jetting data.
Alternatively, when the head-scanning mechanism is adapted to move the head from a waiting position in the main scanning direction, after the head has received the jetting data, and to move back the head to the waiting position again, the part of the time since the previous operation of the recovering unit has been completed may be a time since the head has been moved back to the waiting position again after being moved in the main scanning direction until the head completes receiving the jetting data. In this manner, it is taken into consideration that in the time since the previous operation of the recovering unit has been completed, the receiving time of the jetting data may vary relatively widely depending on the jetting data.
Preferably, the controller may be adapted to control the recovering unit based on the jetting data itself.
In detail, when the head-scanning mechanism is adapted not to move the head to an area over a position to which a last drop of the liquid is jetted in the one scanning movement in the main scanning direction (when a scanning area (scanning columns) may be changed), the controller is preferably adapted to control the recovering unit depending on a distance for which the head is moved in a next scanning movement in the main scanning direction, based on the jetting data corresponding to the next scanning movement. Alternatively, in that case, the controller is preferably adapted to control the recovering unit depending on a distance for which the head has been moved in a previous scanning movement in the main scanning direction.
Alternatively, the controller is preferably adapted to control the recovering unit dependently depending on a distance for which the head is moved until a first drop of the liquid is jetted in a next scanning movement in the main scanning direction based on the jetting data corresponding to the next scanning movement.
Alternatively, when the head has a plurality of nozzles, and the recovering unit is adapted to recover a suitable viscosity of liquid in each of the plurality of nozzles from an increased viscosity thereof, the controller is preferably adapted to control the recovering unit depending on respective distances for which the head is moved until respective first drops of the liquid are jetted from the respective nozzles in a next scanning movement in the main scanning direction, based on the jetting data corresponding to the next scanning movement.
Alternatively, the controller is preferably adapted to control the recovering unit dependently depending on a proportion of the liquid jetted in a previous scanning movement in the main scanning direction.
Alternatively, when the head has a plurality of nozzles, and the recovering unit is adapted to recover a suitable viscosity of liquid in each of the plurality of nozzles from an increased viscosity thereof, the controller is preferably adapted to control the recovering unit depending on respective proportions of the liquid jetted from the respective nozzles in a previous scanning movement in the main scanning direction.
Alternatively, the controller is preferably adapted to control the recovering unit depending on a proportion of the liquid jetted in a next scanning movement in the main scanning direction based on the jetting data corresponding to the next scanning movement.
Alternatively, when the head has a plurality of nozzles, and the recovering unit is adapted to recover a suitable viscosity of liquid in each of the plurality of nozzles from an increased viscosity thereof, the controller is preferably adapted to control the recovering unit depending on respective proportions of the liquid jetted from the respective nozzles in a next scanning movement in the main scanning direction, based on the jetting data corresponding to the next scanning movement.
In addition, when the head has a plurality of nozzles in which a plurality of kinds of liquid are used, respectively, and the recovering unit is adapted to recover a suitable viscosity of liquid in each of the plurality of nozzles from an increased viscosity thereof, the controller is preferably adapted to control the recovering unit based on characteristics of the respective kinds of liquid used in the respective nozzles.
In addition, when the liquid jetting apparatus further includes a sensor for detecting a state of the environment where the liquid jetting apparatus is used, the controlling unit is preferably adapted to control the recovering unit based on an output from the sensor.
In addition, when the liquid jetting apparatus further includes a capping unit capable of being moved between a position away from the head and a position for coming in contact with the head in order to seal the nozzle, the controlling unit is preferably adapted to bring the capping unit in contact with the head based on the time measured by the measuring timer.
The recovering unit may be a minutely-vibrating unit for causing the liquid in the nozzle to minutely vibrate. Alternatively, the recovering unit may be a flushing unit for causing the liquid in the nozzle to jet out from the nozzle outside an objective jetting area.
In addition, a controlling unit for controlling a liquid jetting apparatus includes a head having a nozzle adapted to receive jetting data corresponding to one scanning movement in a main scanning direction. A head-scanning mechanism moves the head in the main scanning direction after the head has received the jetting data. A recovering unit recovers a suitable viscosity of liquid in the nozzle from an increased viscosity thereof. A measuring timer measures at least a part of the time since a previous operation of the recovering unit has been completed. The controlling unit is adapted to control the recovering unit based on the time measured by the measuring timer.
A computer system can constitute the whole controlling unit or only one or more components in the controlling unit.
This invention includes a storage unit capable of being read by a computer, storing a program for constituting the controlling unit in a computer system.
This invention also includes the program itself for constituting the controlling unit in the computer system.
This invention includes a storage unit capable of being read by a computer, storing a program including a command for controlling a second program executed by a computer system including a computer. The program is executed by the computer system to control the second program to constitute the controlling unit.
This invention also includes the program itself, including the command for controlling the second program executed by the computer system including the computer. The program is executed by the computer system to control the second program to constitute the controlling unit.
The storage unit may be not only a substantial object such as a floppy disk or the like, but also a network for transmitting various signals.